Cardiac Output and Shunts Flashcards
What is the gold standard for measuring cardiac output
It is called the Fick method.
The Fick equation states that the amount of blood flowing in the systemic circulation is equal to the rate of consumption of oxygen by the systemic organs divided by the difference of O2 in aterial and venous blood
Normal levels of arterial and venous O2 content at rest
Arteriole is 20 ml O2 /100 ml of blood whereas venous is 15 ml O2/ 100 ml of blood
What is the Fick equation
This will give you blood flow
How do you find the pulmonary bloodflow
Its always oxygenated - deoxygenated
What is he trying to explain here
At steady state the amount of O2 absorbed through the lungs, which can be measured via a spirometer is equal to the amount of O2 consumed by the organs.
O2 content in the pulmonary arteries is the same as O2 content in the vain, given there is no shunt
O2 content in the arterioles is the same as O2 content in the pulmonary vein
How does the pulmonary flow and CO change when there is a shunt? What does the magnitude of the shunt determine
Usually pulmonary blood flow and CO are equal. However they can be different if there is a shunt present. The magnitude of the shunt will determine the difference in the CO and pulmonary flow
Describe how the shunt changes the O2 content depending on its location
Where the shunt originates, there is no change in O2 but some blood flows out of the shunt (so the volume is less but O2 content is the same).
On the other hand where the shunt is opening to it will add more blood and increase the O2 content (I always think of this as from left to right since the pressure on the left is always more than the pressure on the right).
This is how you locate the shunt
What is the key for ventricular septal defect
O2 content increases in the right ventricle, also the volume increases in the right ventricle
What are the 2 effects of Ang II
It causes constriction of systemic arterioles and causes aldosterone to be released which causes retension of water
Relating to the effects of Ang II what does it mean for people with shunts
Their blood volume will be higher than normal since they need a higher CO
Where is all of this extra blood stored
It is in the pulmonary circulation and it can lead to hypertrophy of the right and left ventricles, it can also cause hypertrophy of the left atrium
Atrial Septal defect
O2 content in the right atrium increases which causes increase in O2 content also in the right atrium, this is the key for finding ASD is this
In ASD where is all of the blood stored (or passing through)
How does this represent on EKG
It is stored in the atrias and the right ventricle, causing hypertrophy of the right ventricle which results in right axis deviation seen on EKG
Ductus Arteriosis
Shunt between the aorta and the pulmonary artery
In utero this isnt as much of the problem since there is not a lot of blood going through the lungs
What happens to the baby after birth due to the presence of Ductus Arteriosis
The pressure due to high blood pressure in the aorta causing pulmonary hypertesion which causes right ventricular hypertrophy
Immediately upon birth there is right axis deviation
O2 content stays the same in the heart, pulmonary arteriole contant increases
Where is the extra blood stored
It is in the left side of the heart primarily
